Vol 38, No 5 (2017)

Novel compositions of frost-resistant rubbers (elastomers) are investigated. The possibilities of modifying the basic elastomer using several different fillers are studied. A PTFE-based filler (Forum), technical carbon (TC), and graphene oxide (GO) are tested as fillers. Mechanical, tribological, and microscopic investigations (SEM with elemental analysis and an atomic force microscope (AFM) using different modes) are performed. In order to investigate the operating parameters of these samples, the sample surface was studied before and after the friction tests. The surface topography and the distribution of individual elements over the surface are estimated. Microscopic sections of the samples are studied to obtain information concerning the bulk distribution of the chemical elements. It is shown that the use of fillers such as Forum and technical carbon leads to a better result when they are used together. Their elastic, viscous, and adhesive properties are studied using AFM (the force curve mode—“force-distance curve” and the force modulation mode—“magnitude-distance curve”). It is shown that a distinctive feature of rubber samples having the best tribological properties consists of an increase in rigidity and a decrease in adhesion in the course of tribological testing.

In the article considered the problem of the devastating impact of friction to the machine parts’ and mechanisms, and ways to solve this problem. Described the method of mechanical activation of the graphite grease in a planetary mill. Experimentally determined friction coefficients of sliding of standard and mechanically activated of the graphite grease. Established that as a result of mechanical activation friction coefficient of sliding decreases in the 2.2–2.5 times. The obtained spectra of Raman scattering allow to assume, that the reduction in the friction coefficient of sliding happens at the expense of forming in a graphite grease of graphene nanostructures.

An experimental study of the steel-cutting process in a controlled atmosphere is performed. Based on the results, a theoretical model is developed to evaluate the kinetics of the formation of an oxide lubricating film under steel cutting and to optimize the cutting process by decreasing the cutting forces and the wear and tear of the tool. The performed studies showed that, for the manifestation of an effective lubricating effect of pure oxygen due to the formation of a separating protective film of adsorbed oxygen, it is necessary to maintain a pressure of more than 1.32 Pa.

The results of a study of the wear mechanism of diamond tools for turning aluminum-matrix composite materials (ACMs) hardened by Al₂O₃, SiC, and B₄C particles are presented. The study of the posterior surface topography of a diamond tool (ASPK-2) shows the presence of parallel scratches in the direction of the vector of the cutting speed; it is characteristic of abrasive wear fatigue. Research on the mass-transfer of the elements of the tool material into the chips of the treated material is carried out; it shows the presence of particles of the tool material of a size comparable to the ACM filler microparticles. The model of the abrasive-wear fatigue of a diamond tool during the turning of ACMs, considering the power of the impact of the reinforcement particles, the hardness of the tool depending on the temperature in the cutting zone, the abrasiveness, and the mass fraction of the dispersed particles reinforcing the matrix and tool geometry is proposed.

The comparative analysis of the calculated and experimental data concerning the polytetrafluorethylene thermal loading in friction is carried out. The conditions of achieving the quasi-stationary thermal state of a polymeric sample depending on the sliding distance are shown. The optimum value of the sliding distance taking into account the distribution coefficient of the heat flow according to Sharron’s formula is determined.

The plastic deformation of the discrete contacts of a tool with a circular-arc and an inclined profile with the periodical microroughnesses of the metallic part’s surface layer is modeled. The plane deformation theory of a perfectly plastic body is used. The plastic deformation process of the surface layer’s microroughnesses by a sliding tool with Prandtl’s high contact friction in which the plastic shear occurs in the direction of the slide of the tool, with the microroughnesses’ depressions being filled and a decrease of the surface roughness, is studied.

The mechanism of the formation of adhesive bonds of a friction modifier (a lubricant based on bitumen) with a wheel of railway transport is considered. Calculations performed using quantum chemical methods allow us to draw a conclusion on the existence of the physical adsorption of this lubricant on a wheel surface. The lubrication’s effectiveness can be improved using fatty acids whose introduction into the lubricating material leads to the formation of chemical bonds in the system; this is experimentally confirmed for the contact rotaprint lubrication technology.